Okay, let's break down the possibilities and the code implications of punching a hole between two metal enclosures to use as a raceway.

The Short Answer

Generally, no. Punching a hole and using it as a raceway without proper fittings and listing is a code violation and a potential safety hazard.

The Long Answer and Considerations


Code Violations



NEC 300.12 Mechanical Continuity - Raceways and Cables. This section requires complete raceway systems to provide a mechanically continuous path for the conductors. A hole punched between enclosures without proper fittings doesn't meet this requirement. The transition needs to be secured to both enclosures. NEC 300.10 Electrical Continuity of Metal Raceways and Enclosures. This section requires metal raceways and enclosures to be electrically continuous and securely fastened so as to provide a low-impedance path for ground-fault current. An unsecured hole between boxes won't provide this low-impedance path. NEC 314.17(B) Entering Boxes, Conduit Bodies, or Enclosures

This section (among others in Article 314) dictates how conductors are supposed to enter boxes and enclosures. It requires listed fittings to protect the conductors from abrasion and ensure a secure connection. A punched hole alone won't satisfy this.

NEC 110.3(B) Examination, Identification, Installation, and Use of Equipment

Listed or labeled equipment shall be installed and used in accordance with any instructions included in the listing or labeling. Using an enclosure in a manner not intended by the manufacturer would violate this rule.2.

Safety Hazards



Abrasion

The sharp edges of a punched hole can damage wire insulation over time, leading to shorts, ground faults, and fires.

Lack of Grounding

Improperly connected enclosures may not provide a reliable ground path, increasing the risk of electric shock.

Arcing

If a fault occurs, the lack of a proper, low-impedance ground path can lead to arcing, which is a significant fire hazard.

Penetration

If the enclosures are touching but not grounded to each other, a voltage can develop causing an arc.3.

Acceptable Methods and Materials



Listed Conduit and Fittings

This is the standard and safest approach. Use short lengths of rigid metal conduit (RMC), intermediate metal conduit (IMC), electrical metallic tubing (EMT), or flexible metal conduit (FMC), along with appropriate connectors (couplings and bushings) to connect the enclosures. For example, you could use a short nipple of RMC with locknuts and bushings on both ends to connect the two enclosures. Ensure the conduit is properly grounded.

Close Nipple/Chase Nipple

A very short section of threaded conduit (like RMC or IMC) that allows you to thread into the box using locknuts and insulated bushings.

Factory-Made "Troughs" or Wireways

Some manufacturers produce short sections of raceway or wireway specifically designed to connect enclosures. These are typically listed and provide proper protection and grounding.

Enclosure Manufacturer Accessories

The manufacturers of the enclosure may offer an accessory.

Proper Bonding

Ensure that both enclosures are properly bonded to ground.4.

Fabrication Considerations (and Why They're Problematic)



"Fabricating" something isn't against NEC standards. Not Listed

If you fabricate a fitting yourself, it won't be listed by a testing laboratory (like UL, ETL, etc.). This means it hasn't been tested for safety and suitability for its intended purpose.

Difficult to Guarantee

It's very difficult to fabricate something that meets all the requirements for grounding, mechanical protection, and protection against abrasion.

Inspectors

An electrical inspector is highly unlikely to approve a non-listed, fabricated fitting, especially for a connection between a main distribution panel and another enclosure. They are responsible for ensuring the installation meets code and is safe.

In summary: While it might seem like a simple shortcut, punching a hole between enclosures and using it as a raceway is generally a bad idea from both a safety and code compliance standpoint. Use listed conduit and fittings to ensure a safe and code-compliant installation. Consult with a qualified electrician if you're unsure about the best approach for your specific situation. Flag for review